A number of different types of electronic packages are used to mount integrated circuits and other electronic devices. Such packages are used because they often provide the advantages of physical protection, electrical interconnect, and thermal dissipation for the mounted device. However, thermal fatigue, solder ball creep under compression loading, and other related issues are items of concern due to thermal stresses resultant from variations in thermal coefficients between the various components of the package and its mounted device(s) and due to the nature by which these completed packages are assembled. This is especially the case for the larger area packages.
In order to reduce the risk of a failure in the package, mechanical stops or interposers have been included to provide some support to the package substrate. These designs typically use metal or plastic spacers inserted under the package corners or edges. Since ceramic substrates have a high mechanical strength and can usually withstand the high stresses exerted on the package corners and edges, they may be relatively effective for ceramic packages. However, for other types, such as laminate packages, the substrates cannot withstand the high stresses typically involved in the assembly process. A large mechanical load on the package can easily break the laminate substrate at its corners or edges or can result in excessive warp of the substrate.